Questions & answers about the cause of and cures for indoor stains appearing in streaks or dark lines or in rectangular areas in buildings traced to black or dark thermal tracking or ghosting.

This article series describes & diagnoses the cause of various interior wall and ceiling stains and explains how to recognize thermal tracking, (also called ghosting or ghosting stains or thermal bridging stains), building air leaks, and building insulation defects.

Often these stains are mistaken for toxic indoor mold.

Thermal Tracking or Ghosting Streaks or Lines FAQs

These questions & answers about ghosting or thermal tracking lines and rectangles in buildings were posted originally

at GHOSTING DARK STREAKS or LINES: CAUSES - be sure to see that article.

On 2018-06-13 by (mod) - How can I fix these ghosting or thermal tracking lines and rectangles?

Tany

Please see THERMAL TRACKING REMEDIES for details - at https://inspectapedia.com/interiors/Stain_Remove_Prevent.php -

and let me know if you have further questions.

On 2018-06-13 by Tany

How can I fix this? Who can check if it is an air leak? The roofer after seeing this confirmed that it is not a roof leak and suggested to get it painted.

My concern is if there is an air leak, the stains will come back after sometime even if I paint that ceiling. What can I do to fix this? Thanks

On 2018-06-12 by (mod) -

Tracking stains, associated with the combination of air leaks or voice and insulation and of course an indoor source of dust or switch or debris.

On 2018-06-11 by Tany Could this be thermal tracking?

Hi, I have noticed this strange rectangular stain on my vaulted ceiling recently. I noticed these on a dry day ( no rain for few days). I believe the humidity inside the house was high as no AC was on for 10/15 days.

Could this be thermal tracking? Also when I tried touching those area in a hot sunny day, I felt some points felt warm to touch then the rest of the ceiling.

Same area I touched after a heavy rain, didn’t felt wet, but it didn’t felt warm that day. Any idea if it is due to missing or insufficient insulation on vaulted ceiling?

On 2018-03-29 by Megan - stains after roof damage and high winds

We recently had a nor’easter with extremely high winds. The winds tore a good portion of shingles off our roof and sucked all the attic access doors into the attic.

We noticed vertical lines from ceiling to floor on the interior of every external wall after the storm. All the drywall nails are also dark and the majority are now popped. I should maybe mention it’s a large house with a pellet stove in the basement which was put out by the winds during the storm.

We also have a heat pump with oil back up and a gas fireplace. I read these lines usually appears overtime but they were not there prior to the storm. These lines look identical to pictures posted of thermal tracking. Is this possible?

On 2018-02-06 by (mod) - dark strea

Yes that could be thermal tracking. If exploring convinces you you're not actually missing insulation then the remaining steps are to clean the surface and paint with a sealer and then repaint with a finish coating

On 2018-02-04 by Louise

I live in a manufactured home. I have dark streaks on the ceiling that appear at regular intervals. Can this be thermal tracking? Is there insulation in the ceiling? How do I solve this problem? The previous owner smoked. I am not surd if he smoked inside.

On 2018-02-01 by (mod) - thermal tracking or ghosting stains around recessed ceiling lights - pot lights

Alicia

From your photo I would say it's pretty likely that those recessed ceiling lights have had insulation pulled-back (avoiding an overheating light fixture and fire hazard).

The result is a chimney effect that increases heat loss as well as a cool spot on the ceiling where moisture and dirt adhere - it's a good example of thermal tracking discussed in this article. You show that the spots can appear not just in lines but in whatever pattern of cool area occurs in a ceiling or wall.

If this were my house I would consider installing DCIC-rated ceiling lights so that they can be safely insulated-over, and I would seal the light cutouts against air leakage.

See RECESSED LIGHT CLEARANCES

On 2018-02-01 by Alicia - what are these round patch stains?

We just moved in to this house, that is full of round patches.Can someone Identity the problem.

On 2016-06-17 by (mod) -

Thermal tracking does not mean that there is mold contamination in the same area as the streaks; those are surface depositions of dust from temperature differences + slight moisture differences on the surface.

But if there was a roof leak that sent water into the wall cavity, that needs to be explored.

On 2016-06-17 13:23:37.862543 by Laura

If I have thermal streaks on the wall should I also assume that I have mold in back of the wall, since I have had a leaking roof which is now fixed?

Question: thermal tracking on garage ceiling caused by car exhaust?

(Oct 2, 2014) Sam said:

Wow, what a great resource, thank you so much for all the info! Question: Garage ceiling has this tracking at all the drywall seams. I can see that the ceiling was insulated. Dark spots exactly correspond with the 12" joint compound finishing knife. Could it be that the compound was simply not sealed properly when it was painted? Also, could exhaust from cars cause this-it's nowhere else in the house.

Thanks, I love this site!

Reply:

Sam

I don't think so. More likely the joints are over studs, pipes, or cooler surfaces that pick up a bit more moisture and thus particle deposits thus stains.

Yes car exhaust could be a particle source, also a moisture source. And if the car is burning oil and is left running for some time in the garage these effects would be increased.

Watch out: for potentially fatal carbon monoxide hazards if car exhaust can enter the home or accumulate in the garage.

Question:

(Jan 17, 2012) John Dabbs said:

A friend has black deposits appearing evenly on vertical surfaces at the top of an internal lounge wall, just under the coving. The wall-hung pictures also have severe dirt 'shadows'.

The appearance is similar to that I experienced when I had a de-ioniser in use in my bedroom, but there is none in the friend's lounge but there is a tv and modern wall-hung logfire-effect unit.

Heating is by conventional hotwater radiators. The house is right on the sea front (at Bude) and fully exposed to off-sea winds.

Could the cause be thermopherosis? Caused by deionisation from sea spray? Or what? And what might the solution be? No nearby pollution source that I can identify.

Reply:

John, if by "appearing evenly" you mean at even spaces or intervals such as marking the intervals of building framing members, that would be a classic diagnostic clue indicating thermal tracking.

And yes, using a "de-ioniser" (more likely it was an ionizer - a device that puts an electrical charge on dust particles, causing them to plate out on wall and other building surfaces) can contribute to soot and thermal dust tracking stains on building walls and ceilings.

I'm not sure of the role that off-sea winds would play in thermal tracking - it depends ... for example on the effect of winds on building heat loss. Sea spray itself sounds an unlikely cause to me as I don't imagine much sea spray enters the building interior.

Even common house dust will be enough of a particle source to explain thermal tracking in buildings, but where there are additional dust or particle sources the effects will appear more rapidly and at more extreme levels. Examples include an oil burner that is not working properly, producing soot; use of candles, scented candles, woodstoves, fireplaces, or even burning cooking materials. Pets can also be contributors.

The solution to thermal tracking includes:

- identify and remove sources of high levels interior dust or particulate debris as much as possible

- identify locations of building air leaks and heat losses and correct them

- add insulation, particularly where there are voids

- monitor and correct high levels of interior moisture

Reader follow-up:

Many thanks indeed, Dan, for your comments. Perhaps I should have said that the staining is "uniformly" spread ie a consistent level along the upper perimeter of the room, graduating in intensity as the ceiling is approached. The wall construction is, I believe, solid masonry (I'll check that), and the effect is apparent on all walls whether internal or not. One wall - facing the sea - has a large double-glazed sliding patio door and a "soot" film appears on this after only a few days after cleaning.

Yes, I should have referred to an ioniser - I apologise! It was because of the similarity of this problem to my previous experience with one of these that I was wondering if this was due to an ionising effect somehow. Hence I was wondering if excessive sea spray could cause ionisation? Clutching at straws?

The household has a cat, but it's a large, open house. The room is clean with few furniture pieces, all modern, with a fitted carpet. There are a few nearby properties, all as far as I know with natural gas heating. Completely residential area, and I can't identify an probable sources of dirt/soot particles, but I'll have another look around.

No woodfires, candles or oil burners. Two of the walls have hot water radiators fixed to them, but the staining is at the same level on a third wall with no heating fixed to it.
Any further thoughts?

Question:

(Feb 26, 2012) Jerry said:

How do I clean painted wall from streaking

Reply:

Jerry, identify the cause, fix that source first; then wash and seal and paint the walls. You might want to use a lacquer primer sealer for best results.

Question:

Apr 7, 2012) sue white said:

we have a friend with a house that has ghosting at the 2nd floor ceiling and top 1-2' of wall where it meets the ceiling; the nails are also popping at this ceiling/wall juncture. the house is entirely electric with exception of a gas fired stove in the lower level of the split level home.

do you think the ghosting is due to a malfunction with the stove or some other issue? thank you

Reply:

Not likely - but

Watch out: a gas cook stove that is making visible soot is not working properly and is unsafe, risking fatal carbon monoxide poisoning.

Question: how do I get rid of thermal tracking?

(Feb 20, 2014) Anonymous said:

how does one get ride of thermal tracking.

Reply:

Good question, Anon.

First, the actual black sooty marks can be removed by cleaning washable surfaces; typically we use a non-sudsing detergent. On carpets the carpet would have to be shampooed.

But to complete the "get rid of thermal tracking" process we need to look at what is causing the soot or dust marking and address the underlying causes (which are discussed in this article series).
As some examples:

- look for and fix any extra sources of dust or soot like a poorly-tuned oil burner, use of a fireplace, scented candles, smoking

- check the indoor humidity level and if it's too high we need to fix moisture sources or dehumidify the building - see HUMIDITY LEVEL TARGETS

- See THERMAL TRACKING REMEDIES for complete details

Question:

(Feb 24, 2014) Sarah said:

My husband and I just notified a stain on the ceiling that wasn't there 7 months ago when we moved in. It's a light pinkish tan stain on a textured ceiling.

It is about 3 ft shy of an air vent in our breakfast nook. It does look like a type of moisture stain but nothing similar to your mold patterns you've posted pictures of on the website. This is a ceiling below our guest bath. Any ideas?

Reply:

Sarah, I'd have to see some sharp photos (you can use our CONTACT link if you like);

Generally the location and size of a ceiling stain will suggest something about possible sources, e.g. a possible leak from above.

Question: dark marks forming on our ceilings in winter

4/2/14 Kathy said:

we have been experiencing the same we moved to a house 2 yrs ago and especially during the winter it seems to get darker marks. this winter we noticed it a lot more. I have pictures but unsure how to load them here. we see the ceiling marks by the beams as well as the corner marks or above the heat. should we be concerned?

Reply:

You can use the CONTACT link at page bottom to send us photos. I'll take a look.

Question: thermal tracking stains on carpet in the middle of a room?

(Oct 7, 2014) Brennan said:

Have you ever seen this in carpet in the middle of a room (not near the baseboards). I received a moisture meter to check some ceiling stains to see if they were active or inactive after the former owner replaced the roof. I was using the moisture meter to check the basement- all surfaces.

I found some areas in the basement carpet where the moisture meter was high but dry to the touch. I run a humidifier in that room and it doesn't work very hard to maintain 45-50 rh%

It has a 'line' type stain. A bit darkened (carpet is grey, so this is darkish grey), but not like the other areas where there is actual infiltration soiling (I have seen it is one room near the baseboards but is completely dry). My home is old, so of course it has air leaks.

The former owners had a couch over this area, so I thought it was due to that. Adjacent staining is yellow coloring and also shows moisture in the meter. So moisture and a line/ghosting in carpet. The carpet is gross anyway, so I thought about peeling it back to see if there is a crack in the slab (60+ yr old house).

A contractor friend, without seeing it, said it was radon gas escaping. That seemed like a stretch, since Radon is colorless. I think though, perhaps he meant, air is feeding through the crack and depositing soil on the carpet.

If I do find a crack- should is seal it with concrete/caulk and re-carpet and be vigilant about dehumidification?

Reply:

Brennan

A couple of points to consider:

Most moisture meters, if we exclude thermal imaging, rely on measuring differences in electrical resistance to detect moisture. But other contaminants or materials can also decrease resistance in an area of building material. So not every reading variation is necessarily truly detecting moisture. Some attention, particularly looking for possible moisture sources, are key.

Both pin type moisture meters (Delmhorst for example) and electronic moisture meters (such as some Tramex meters) can be fooled by metal nearby: pipes, foil faced insulation, wiring.

Second: no moisture meter, nor thermal imaging device, can detect old leaks that have since dried, even though the leak might have initiated a building problem with rot, insect damage, or mold contamination.

This is why we argue that reliance on meters and imaging alone for water or mold detection are unreliable. But the instruments are indeed useful, in thoghtful hands. And neat too.

See THERMAL IMAGING, THERMOGRAPHY

(Oct 9, 2014) Brennan said:

Thanks for your comment. One thought (using my science background) was that the moisture meter gives a high reading on what looks like an old dog urine stain (former owner had dog). I had the thought that these left over salts and ions from the urine might act as a weak conductor and activate the moisture meter.

On the internet, it seems that carpet companies use moisture meters to find hidden pet stains, because the salt from the urine can draw moisture from the air (or even just the natural evaporation of the concrete slab). So, thanks for your help. I tend to over-think things. I agree, it is a neat tool.

(Oct 9, 2014) (mod) said:
Interesting Brennan, and thoughtful. I agree with the salts / ions theory for both of the reasons you offer.

It's not over-thinking. The more we understand the better we can find and fix or prevent aggravations. Thanks.

...

Continue reading at GHOSTING DARK STREAKS or LINES: CAUSES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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